This application claims the benefit of Korean Patent Application No. 2001-62668 filed on Oct. 11, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a disc cartridge accommodating a disc which is an information recording and/or reproducing medium, and more particularly, to a disc cartridge in which dust therein can be efficiently discharged.
2. Description of the Related Art
Referring to FIG. 1, a typical disc cartridge 10 accommodating a disc D used in a disc drive 20 includes upper and lower cases 11 and 12 forming an inner space where the disc D is accommodated, and a shutter 13 which selectively opens or closes an opening 12a formed in the lower case 12 so that an optical pickup 21 of the disc drive 20 can access the disc D. Reference numeral 22 denotes an opening lever installed in the disc drive 20 to open/close the shutter 13. As the cartridge 10 enters the disc drive 20, an end portion of the opening lever 22, as shown in FIGS. 2A and 2B, is rotated by being caught by a hooking step 13a of the shutter 13, to thereby open the shutter 13.
The most important reason for using the disc D in the cartridge 10 is to protect the disc D from foreign material such as dust. That is, because, in the case of using a high density disc, foreign material such as dust adhering to the surface of the disc D is more likely to prevent accurate signal processing during recording or reproduction of data on/from the disc. Accordingly, the disc is used by being accommodated in the cartridge 10 to prevent such contamination. Nevertheless, it is unavoidable that some dust still flows into the cartridge 10 through the opening 12a because the shutter 13 necessarily opens inside the disc drive 20 to allow the optical pickup 21 to access the disc D. Although the dust flowing inside the cartridge 10 may exit the cartridge through the opening 12a, a large amount of dust remains inside the cartridge 10.
FIG. 3A shows the result of a simulation of the pattern of air flow formed inside the cartridge D as the disc D rotates. FIG. 3B shows the result of a simulation of a path along which dust particles flowing in the cartridge D are moved by the air flow. Here, it is assumed that the disc D rotates at a velocity of 5,000 r.p.m. counterclockwise and that the density and diameter of the dust particles are about 0.6 g/cm3 and 1 xcexcm, respectively. First, as shown in FIG. 3A, as the disc D rotates at the above stated velocity, the flow of air is formed in the cartridge 10 according to the direction in which the disc D rotates. Since the disc D rotates counterclockwise at a high velocity, air flow outside the cartridge 10 is drawn inward at the left side of the opening 12a due to a difference in pressure while part of the air flow inside the cartridge 10 is discharged at the right side of the opening 12a due to a centrifugal force. The dust flowing into the cartridge 10, in which the air flow is formed as stated above, rotates along with the air flow and creates a path as illustrated in FIG. 3B. Here, it can be seen that the dust is moved toward the opening 12a after rotating inside the cartridge 10 about two turns. The dust flowing in the cartridge 10 through the left side of the opening 12a is not discharged through the right side of the opening 12a after rotating only one turn, and therefore usually remains inside the cartridge 10 for a time of more than one turn. That is, the velocity at which the dust is discharged from the cartridge 10 is less than half of the velocity at which the dust flows into the cartridge 10. Accordingly, the amount of dust remaining in the cartridge 10 gradually increases. The difference between the flowing-in velocity and the discharge velocity is inversely proportional to the size of a dust particle. This is because the smaller the mass of the dust particle, the less a centrifugal force needed for discharging a dust particle from the cartridge 10 through the opening 12a. 
To solve the above problems, a method of installing an additional filter in the cartridge 10 has been proposed. However, when the filter is used for a long time, it becomes saturated, and inconveniently needs to be replaced repeatedly. If the filter is not timely replaced, the dust collected by the filter may contaminate the disc D. Thus, an improved structure by which dust in the cartridge can be appropriately discharged from the cartridge without using an additional filter is required.
Accordingly, it is an object of the present invention to provide an improved disc cartridge which can effectively discharge dust introduced externally by using the flow of air produced during the rotation of a disc.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention are achieved by providing a disc cartridge comprising a case to accommodate a disc, a shutter to open or close an opening formed in the case to enable a recording and/or reproducing operation with respect to the disc, a discharge path provided at one side of the case to allow the flow of air formed therein during rotation of the disc, and an opening/closing mechanism to open/close the discharge path.